Re: [spi-devel-general] adding bits_per_word to struct spi_board_info to mirror struct spi_device

From: Mike Frysinger
Date: Mon May 07 2007 - 19:47:57 EST


On 4/25/07, David Brownell <david-b@xxxxxxxxxxx> wrote:
On Wednesday 25 April 2007, Mike Frysinger wrote:
> the spi_device structure has a bits_per_word so that you can change
> the value on a per-device setting, yet the spi_board_info structure
> does not ... this means that the bus-specific structure has to have a
> bits_per_word member which the spi bus driver will copy into the spi
> device bits_per_word member

Actually that's more likely a driver-specific characteristic than
something related to board wiring/configuration ... a characteristic
of the particular protocol requests being made. That's why for
example bits_per_word has a per-transfer override, and drivers are
able to call spi_setup(spi).

hmm, true ...

> is there something obvious i'm missing ? seems to me that if the
> generic spi framework respects bits_per_word on a per-spi device
> basis, then it should be exposed in the generic info structure so that
> the setting can be tracked in the boards file ...

The initial driver set didn't need it, that's all. ISTR someone
else pointed out this quirk, but never provided a patch to resolve
the issue.

so which direction should it be ? or should it be both ? :)

Blackfin at the moment is doing DMA/bits_per_word setup in the boards
... we could move these to the drivers and have each one just call
spi_setup() at init, or i could post a patch for the common framework
if you think that's an OK direction to [also] go ...
-mike
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